At the final whistle, the visiting Leicester City supporters were singing a Christmas chorus they barely anticipated unleashing at a ground where the home side have been unbeaten all season.

"Jingle bells, jingle bells, jingle all the way, oh what fun it is to see City win away," they sang in delight.

And the Yuletide sense of goodwill can only have been enhanced by the fact that there was nothing fortunate about the three points that were popped into Leicester stockings. This was as shrewd, professional and well organised an away victory as could be imagined. Won with a scintillating goal from Jamie Vardy, for the visiting fans it was the kind of performance all too rarely seen since those title-winning times of 2015-16.

For Maurizio Sarri, on the other hand, it was a sobering start to the festive rush. His Chelsea side were outfought, out-thought and out-manoeuvred, their lack of precision demonstrated at the last by the substitute Cesc Fabregas launching a forlorn, injury-time long ball that drifted over the heads of his forwards into the hands of a grateful Kasper Schmeichel. While their effort could not be faulted, Chelsea spent much of the afternoon looking befuddled and bemused.

It had started well enough. All quick interchanges and sharp passing, led by the relentlessly inventive Eden Hazard, the home side soon dominated the early possession. Hazard suggested what might come when he deftly spun away from Harry Maguire. But, under pressure from Wes Morgan, flying in to block, he shot against the bar. Jorginho then forced a fine save from Schmeichel and Willian should have done better after a turbo-powered breakaway by N'Golo Kante found him in space in the area.

Yet clear opportunities were as sparse as seasonal snow. Indeed, despite Chelsea's overwhelming lead in the possession stats, the visitors were their equal in genuine chances. Their best in the first half came when Wilfred Ndidi unleashed a howitzer of a volley from the edge of the area which appeared to be destined for the top corner. Kepa Arrizabalaga, however, had other ideas, arcing his back and tipping the ball over.

The longer the game went on, the more obvious it was that Leicester were not to be remotely intimidated by Chelsea's ineffectual huff and puff. And with Hamza Choudhury providing an impenetrable defensive shield, James Maddison began finding more and more space all around the pitch.

To his left, Ben Chilwell, too, was having a seasonal romp. Every time a home attack fizzled out (and that was frequently), Schmeichel would find the England full-back, who would power forward. Increasingly he did not wait for his goalkeeper and stepped in to seize possession himself. One fizzing run consumed most of the length of the pitch, until the ever-tireless Kante finally caught up and tackled him.

It was in the 51st minute that the Leicester approach found perfect expression. After yet another Chelsea attack had fizzled out, the adventurous Ricardo Pereira galloped forward. He moved the ball inside to Maddison, who using the space opened up by Antonio Rudiger's unfortunate tumble, played the most sublime of disguised passes through for Vardy.

It was the kind of ball the ferret-like forward thrives on and, with minimal backlift, he swished a glorious shot into the roof of the net. Accurate, ruthless, clinical: it was everything Chelsea had not been.

Chelsea's Eden Hazard shoots at goal. Photo: Hannah McKay/Reuters

If the home support expected an immediate response, none came. The goal seemed to cow the Chelsea team, push them on to the back foot, befuddle the thinking.

"After the goal, the reaction was strange," said Sarri. "(We reacted) not in the right direction, not as a team, but as 11 different players. We could have done better. We had only to continue to play as in the first part of the match. There was time to score. There was mental confusion."

In victory Puel, meanwhile, had a very different analysis of what had just happened from his opposite number.

"If Chelsea didn't perform today I think my players were responsible," he said. He had a point. There is only one verdict on what had happened: Chelsea were outfoxed.